Acceleration of solar wind particles by traveling interplanetary shocks

The acceleration of thermal solar wind protons at spherical interplanetary shocks driven by coronal mass ejections is investigated. The solar wind velocity distribution is represented using $\kappa$-functions, which are transformed in response to simulated shock transitions in the fixed-frame flow speed, plasma number density, and temperature. These heated solar wind distributions are specified as source spectra at the shock from which particles with sufficient energy can be injected into the diffusive shock acceleration process. It is shown that for shock-accelerated spectra to display the classically expected power-law indices associated with the compression ratio, diffusion length scales must exceed the width of the compression region. The maximum attainable energies of shock-accelerated spectra are found to be limited by the transit times of interplanetary shocks, while spectra may be accelerated to higher energies in the presence of higher levels of magnetic turbulence or at faster-moving shocks. Indeed, simulations suggest fast-moving shocks are more likely to produce very high-energy particles, while strong shocks, associated with harder shock-accelerated spectra, are linked to higher intensities of energetic particles. The prior heating of the solar wind distribution is found to complement shock acceleration in reproducing the intensities of typical energetic storm particle events, especially where injection energies are high. Moreover, simulations of $\sim$0.2 to 1 MeV proton intensities are presented that naturally reproduce the observed flat energy spectra prior to shock passages. Energetic particles accelerated from the solar wind, aided by its prior heating, are shown to contribute substantially to intensities during energetic storm particle events.Comment: 26 pages, 21 figures, 5 tables. Accepted for publication in the Astrophysical Journa

Mixed-Mode Sensitivity Analysis of a Combined Differential and Common Mode Active Receiving Antenna Providing Near-Hemispherical Field-of-View Coverage

A theoretical framework for a mixed differential and common mode sensitivity analysis of active receiving antennas is presented, which includes the derivation of a novel set of noise parameters for dual-mode balanced amplifiers. The analysis is applied to an example of a mixed-mode active wire antenna design, consisting of an integrated monopole and dipole structure. Results of numerical simulations and experimental measurements are presented which show that, for a single-polarized design, the judicious use of both differential and common modes enables the field-of-view coverage to be extended over the entire hemisphere with a variation in receiving sensitivity of less than 3 dB in the E-plane

Quad-Mode Antenna for Wide-Scan Sparse Arrays

A conical quad-mode antenna excited through four orthogonal transverse electromagnetic modes is presented. The radiation characteristics of each mode are validated through measurements, illustrating the complimentary nature of the four far-field radiation patterns through which near-hemispherical field-of-view coverage can be achieved

Thermal simulation of magnetization reversals for size-distributed assemblies of core-shell exchange biased nanoparticles

A temperature dependent coherent magnetization reversal model is proposed for size-distributed assemblies of ferromagnetic nanoparticles and ferromagnetic-antiferromagnetic core-shell nanoparticles. The nanoparticles are assumed to be of uniaxial anisotropy and all aligned along their easy axis. The thermal dependence is included by considering thermal fluctuations, implemented via the N\'eel-Arrhenius theory. Thermal and angular dependence of magnetization reversal loops, coercive field and exchange-bias field are obtained, showing that F-AF size-distributed exchange-coupled nanoparticles exhibit temperature-dependent asymmetric magnetization reversal. Also, non-monotonic evolutions of He and Hc with T are demonstrated. The angular dependence of Hc with T exhibits a complex behavior, with the presence of an apex, whose position and amplitude are strongly T dependent. The angular dependence of He with T exhibits complex behaviors, which depends on the AF anisotropy and exchange coupling. The resulting angular behavior demonstrates the key role of the size distribution and temperature in the magnetic response of nanoparticles.Comment: Revised arguments in Introduction and last sectio

Beyond the Planar Limit in ABJM

In this article we consider gauge theories with a U(N)X U(N) gauge group. We provide, for the first time, a complete set of operators built from scalar fields that are in the bi fundamental of the two groups. Our operators diagonalize the two point function of the free field theory at all orders in 1/N. We then use this basis to investigate non-planar anomalous dimensions in the ABJM theory. We show that the dilatation operator reduces to a set of decoupled harmonic oscillators, signaling integrability in a nonplanar large N limit.Comment: v2: minor revisison

Amniotiese Bande by 'n Baba na Abdominale Swangerskap

A baby, delivered by Caesarean section after a 36-week extra-uterine pregnancy, with deformities due to amniotic bands, is described. The mechanism of amniotic band deformities and the paediatric risks of extra-uterine pregnancy are briefly discussed.S. Afr. Med. J., 48, 1106 (1974

Amniotiese bande by 'n baba na abdominale swangerskap

A baby, delivered by Caesarean section after a 36-week extra-uterine pregnancy, with deformities due to amniotic bands, is described. The mechanism of amniotic band deformities and the paediatric risks of extra-uterine pregnancy are briefly discussed.S. Afr. Med. J., 48, 1106 (1974)

Semiclassical Strings, Dipole Deformations of N=1 SYM and Decoupling of KK Modes

In this paper we investigate the recently found $\gamma$-deformed Maldacena-Nunez background by studying the behavior of different semiclassical string configurations. This background is conjectured to be dual to dipole deformations of $\N=1$ SYM. We compare our results to those in the pure Maldacena-Nunez background and show that the energies of our string configurations are higher than in the undeformed background. Thinking in the lines of (hep-th/0505100) we argue that this is an evidence for better decoupling of the Kaluza-Klein modes from the pure SYM theory excitations. Moreover we are able to find a limit of the background in which the string energy is independent of $\gamma$, these strings are interpreted as corresponding to pure gauge theory effects.Comment: 31 pages, references added, new solutions in Section 7 presented, an appendix added, to appear in JHE

The AdS 3 × S 3 × S 3 × S 1 worldsheet S matrix

We investigate type IIB strings on AdS 3 × S 3 × S 3 × S 1 with mixed Ramond–Ramond and Neveu–Schwarz–Neveu–Schwarz flux. By suitably gauge-fixing the closed string Green–Schwarz action of this theory, we derive the off-shell symmetry algebra and its representations. We use these to determine the non-perturbative worldsheet S matrix of fundamental excitations in the theory. The analysis involves both massive and massless modes in complete generality. The S matrix we find involves a number of phase factors, which in turn satisfy crossing equations that we also determine. We comment on the nature of the heaviest modes of the theory, but leave their identification either as composites or bound-states to a future investigation